LWGEOM_pointn_linestring()

Datum LWGEOM_pointn_linestring

(

PG_FUNCTION_ARGS

)

Definition at line 552 of file lwgeom_ogc.c.

{
        GSERIALIZED *geom = PG_GETARG_GSERIALIZED_P(0);
        int where = PG_GETARG_INT32(1);
        LWGEOM *lwgeom = lwgeom_from_gserialized(geom);
        LWPOINT *lwpoint = NULL;
        int type = lwgeom->type;
 
        /* If index is negative, count backward */
        if( where < 1 )
        {
                int count = -1;
                if ( type == LINETYPE || type == CIRCSTRINGTYPE || type == COMPOUNDTYPE )
                        count = lwgeom_count_vertices(lwgeom);
                if(count >0)
                {
                        /* only work if we found the total point number */
                        /* converting where to positive backward indexing, +1 because 1 indexing */
                        where = where + count + 1;
                }
                if (where < 1)
                        PG_RETURN_NULL();
        }
 
        if ( type == LINETYPE || type == CIRCSTRINGTYPE )
        {
                /* OGC index starts at one, so we substract first. */
                lwpoint = lwline_get_lwpoint((LWLINE*)lwgeom, where - 1);
        }
        else if ( type == COMPOUNDTYPE )
        {
                lwpoint = lwcompound_get_lwpoint((LWCOMPOUND*)lwgeom, where - 1);
        }
 
        lwgeom_free(lwgeom);
        PG_FREE_IF_COPY(geom, 0);
 
        if ( ! lwpoint )
                PG_RETURN_NULL();
 
        PG_RETURN_POINTER(geometry_serialize(lwpoint_as_lwgeom(lwpoint)));
}

References CIRCSTRINGTYPE, COMPOUNDTYPE, geometry_serialize(), LINETYPE, lwcompound_get_lwpoint(), lwgeom_count_vertices(), lwgeom_free(), lwgeom_from_gserialized(), lwline_get_lwpoint(), lwpoint_as_lwgeom(), and LWGEOM::type.

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